Objective: To develop a GC-MS/SIM method for the determination of ephedrine and pseudoephdrine and study the
pharmacokinetics
of the two detected components in human plasma. Methods: Gas chromatography-mass spectrometry with selected ion monitoring (GC-MS/SIM) was used. Chromatography/mass spectrometry conditions were: capillary column HP-5(25m×0.2mmID), Helium as carrier gas, with 1.0ml/min runoff, non-split injection , column initial temperature 80℃,after 1 min rising to 200 ℃ at the rate 10℃/min, and then rising to 240℃ at the rate of 20℃/min and holding for 5 minutes. Choosing SIM (m/z=154,265) and injection volume(1μl). Results: The calibration curves of E were linear in the range from 5 ng/ml to 1000 ng/ml (r=0.9985) and 2.5 ng/ml to 500 ng/ml (r=0.9994),the lowest detectable concentrations were 2ng/ml, 1 ng/ml (S/N=3), the recoveries added samples were from 107.5% to 96.2%, and from 102.5% to 93.9% for ephedrine and
pseudoephedrine , respectively. The RSDs of interday and intraday were all less than 10%. The ephedrine and pseudoephedrine in tissue solution were steady within 60 days. The difference of the proportion main
pharmacokinetics between ephedrine and pseudoephedrine parameters is significant. Conclusion: This method is precise and reliable to study ephedrine and pseudoephedrine in human plasma.